The technical scope of the invention is that of priming devices for an explosive charge, and notably for a shaped charge.
Known priming devices generally comprise at least one pyrotechnic igniter and at least one igniting relay placed between the igniter and an explosive load.
One of the problems encountered with known priming devices is the difficulty of ensuring the accurate centering of the pyrotechnic igniter with respect to the charge body.
More particularly, in the case of shaped charges, the detonation wave that is propagated in the charge must be perfectly symmetrical with respect to the charge axis.
Such a symmetry enables the optimal displacing or deformation of the shaped charge liner (slug or hollow charge). Even slight asymmetry (for example of around a few tenths of a millimeter) risks causing a reduction in effectiveness of the shaped charge.
Moreover, in the field of self-destruct charges for ballistic missiles, it is customary to include back-up priming means so as to reduce this risk of failure of the self-destruct system.
The multiplication of priming means thus raises the problem of producing a priming wave that is symmetrical and this whatever the position of the igniter being activated.
The aim of the invention is to propose a priming device that overcomes such problems and does not suffer from the drawbacks of known devices.
Thus, the priming device according to the invention ensures the ignition of an explosive charge along the charge axis whatever the position of the igniter or igniters with respect to said axis.
The invention thus makes it possible to obtain priming symmetry, using simple means.
Thus, the invention relates to a safety priming device for an explosive charge, notably a shaped charge, comprising a pyrotechnic igniter and at least one igniting relay placed between the igniter and an explosive load of the charge, wherein the igniting relay comprises means enabling the detonation wave produced by the igniter or igniters to be re-centered along the charge axis, said means comprising a confinement block having a bore converging between an external face positioned on the said having the igniter or igniters and an inner face positioned beside the explosive load, said bore filled with a relay explosive, the confinement block comprising means to prevent the propagation of a shock wave axially through the confinement block between the igniter or igniters and the explosive load.
According to a first embodiment of the invention, the confinement block may be made of an organic material having acoustic impedance that is less than 15.106 kg/m2s, this material constituting means to prevent the propagation of a shock wave through the confinement block.
According to a second embodiment of the invention, the confinement block may incorporate at least one collar that will be placed in the vicinity of the igniter or igniters and which will be followed by a free space surrounding the block, said free space constituting means to prevent the propagation of a shock wave axially through the confinement block.
This free space may be formed by a cylindrical groove delimited by two collars.
The bore in the confinement block may incorporate at least one conical part having a half-angle at the apex of between 10 and 25xc2x0, the small diameter of the cone being of between 2 and 5 mm and the large diameter of the cone being of between 13 and 30 mm.
The igniting relay may comprise a first layer of relay explosive applied to the confinement block and placed between the igniter or igniters and the confinement block.
The confinement block will be generally cylindrically shaped and arranged in a body.
The first relay layer may be of a thickness of at least 2 mm.
The first layer of relay explosive may be ring-shaped or else may be in the shape of a substantially rectangular tongue.
Advantageously, the device may comprise at least two pyrotechnic igniters placed at a distance from the charge axis.
A further subject of the invention is a shaped charge incorporating a safety priming device having at least two igniters and having the same performances whichever igniter is activated.
Such a charge may be used notably to ensure the destruction function during the trajectory for ballistic projectiles or for their payload.
In this case, this charge may advantageously be an explosively-formed charge.